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1. Technical Field
This invention relates to aqueous liquid cleaning and antimicrobial compositions which leave a low residue of material on the surface to be cleaned. The compositions of the present invention contain a synergistic combination of specific amounts of certain organocarboxylic acids and sparingly water-soluble monohydric aliphatic alcohol solvents, such as benzyl alcohol and certain low molecular weight glycol ethers. Anionic sulfated or sulfonated surfactants and co-solvents are also included in the preferred compositions.
2. Background Art
Eliminating pathogenic micro-organisms on various surfaces, especially hard surfaces where such organisms may stay active for relatively long periods of time, continues to be a desire of consumers. Traditionally, quaternary ammonium compounds, high levels of certain alcohols, and oxidizing agents have been used in anti-microbial household cleaning products. Disadvantages of utilizing these types of agents include their tendency to cause eye and skin irritation, unpleasant odor, high levels of volatile organic compounds (VOC""s), and potential surface damage effects. Some types of hard surfaces, notably glass, glazed ceramic, and polished metal present an additional problem for cleaning and disinfecting. The visible appearance of these surfaces after cleaning is negatively affected by residues left on the surface by the cleaning composition, even after wiping by the user. Rinsing the surface with fresh water after cleaning would help remove these unsightly residues, but this step adds additional work to the cleaning process. Thus, there exists a need for cleaning and disinfecting compositions which can be used on various hard surfaces, especially glass, glazed ceramic, and polished metals, without leaving unsightly residues. Additionally, it is advantageous that such compositions are comprised largely of water, avoiding the use of large amounts of alcohols such as ethanol or isopropanol for reasons of cost, safety, and minimization of formulation VOC""s.
Certain acids are known to have antimicrobial properties and are recognized as antimicrobial agents by governmental agencies such as the United States Environmental Protection Agency. For example, using the National Pesticide Information Retrieval System (Center for Environmental and Regulatory Information Systems, Purdue University, West Lafayette, Ind.), one can search a database of current US EPA disinfectant registrations. Such a search will indicate that substances such as citric acid, hydrochloric acid, lactic acid, phosphoric acid, propionic acid, and sulfuric acid are EPA recognized antimicrobial actives.
Many current anti-bacterial acid compositions in food and industrial sanitizing applications tend to utilize dilutable concentrates, some of which employ strong acids such as hydrochloric, phosphoric, organophosphonic, sulfuric, or organosulfonic acids. However, the use of cleaning compositions containing strong acids, especially phosphorous-containing acids, is undesirable for the formulation of household cleaning products for consumer use. Weak organic acids are desirable, such as lactic acid and citric acid, and are recognized by the United States Environmental Protection Agency as antimicrobial actives. Because they are weak acids, they are generally safer to use than mineral acids, both for the user and the surfaces to which they are applied. However, these acids generally do not have strong antimicrobial properties when used by themselves at low levels in aqueous solutions. Ideally, a second agent must be employed in combination with low levels of such weak acids, such that this second agent enhances the antimicrobial activity of the composition and also does not contribute to unsightly residue left on the surface after cleaning.
It is also known that certain acid-anion surfactant combinations can be used to formulate anti-microbial cleaners and surface treatments. For example, acid-anionic sanitizers have been successfully used in various industrial antimicrobial applications, such as in the food processing equipment and dairy industries. Non-volatile surfactants are used in these formulations, and therefore will remain on the surface to some extent once applied, unless rinsed away with clean water. Optimum efficacy is usually obtained at a pH of 3 or less. To avoid corrosion problems, and to minimize safety concerns, a pH range of from about 2 to 3 is preferred, which also provides some cleaning efficacy against low to moderate levels of hard-water soiling or spotting.
The prior art includes many compositions for cleaning hard surfaces, some of which include acidic antibacterial, or antimicrobial, components. Among these, U.S. Pat. No. 3,969,258, of Carandang, et al, teaches low foaming acid sanitizer compositions containing anionic surfactants which normally exhibit high-foaming characteristics. A foam suppressant combination of a C8 to C18 aliphatic alcohol, or a C9 to C12 alkyl phenol, and a polyvalent metal salt is present, and additional solubilizing glycols and alcohol may also be present. The reference, however, indicates that a pH of below 3.5 is necessary to achieve the desired result, and while weaker acids such as citric acid may be used, a stronger acid is normally used in combination therewith to achieve the pH desired.
Ramachandran, in U.S. Pat. No. 3,915,633, teaches a pre-wash combination utilizing as its primary active ingredient an organic acid capable of complexing stain-forming metallic ions in soil on a fabric. The organic complexing acid is selected from citric acid, succinic acid, tartaric acid, maleic acid, fumaric acid, and mixtures thereof, in concentrations of from 1 to 20 percent.
Baker et al, in U.S. Pat. No. 4,690,779, teach a substantially non-streaking, hard surface aqueous cleaning composition comprising from about 0.05% to 25.0% surfactant; from about 0.05% to 25.0% of an unbranched straight chain polymer of molecular weight less than 5000; from about 0.05% to 25.0% of an aqueous solvent; from about 0.05% to 25% builder; and the remainder water. Thus, the cleaner of this reference comprises a surfactant, a polymer, a solvent, and a builder, in addition to water.
A liquid hard surface cleaner having disinfectancy, comprising pine oil and organic oil soluble acids at an acid pH, is taught by Spaulding, et al, in U.S. Pat. No. 4,867,898. The reference teaches the use of organic oil soluble acids such as benzene carboxylic acids or hydroxy carboxylic acids, in combination with the pine oil and optional detergent agents.
Brown-Skrobot, et al, in U.S. Pat. No. 4,975,217, teach germicidal compositions for direct application to human skin, including an organic acid and a surfactant as active agents, and optionally also use an alcohol. The composition is intended for use in lotions and sprays, as well as in cleansers.
Eggensperger, et al, in U.S. Pat. No. 5,122,541, teach an aqueous surface disinfectant composition comprising as essential components a mixture of ethyl alcohol and isopropyl alcohol, a mixture of anionic surfactants, and a pH modifying agent to provide a pH from about 2 to 6, or from about 8 to 12.
In U.S. Pat. No. 5,436,008, Richter et al. teach that a microbial composition comprising a major portion of carrier and an effective sanitizing amount of octanoic acid or octanoic acid derivatives, and a sulfur containing compound, may be used for dairy farms, food and beverage processing plants, kitchens, food serving establishments, and for general utility in domestic households.
In addition to the above, U.S. Pat. No. 5,750,482, of Cummings, teaches a non-streaking glass cleaning composition comprising an ethylene glycol monohexyl ether, a surfactant, an organic cosolvent comprising a mixture of a low boiling organic cosolvent and a high boiling organic cosolvent, a builder, and water, said composition effective in a pH range from about 3.5 to about 11.5 as a glass cleaning composition.
To minimize expense and possible visible detrimental effects of antimicrobial compositions on surfaces to be treated, it is desirable to minimize the amount of antimicrobial agent left on a surface after cleaning, while still retaining efficacy against pathogenic micro-organisms, such as Staphylococcus aureus and Klebsiella pneumoniae. For acid-based biocidal chemistries to be used by consumers, it is also desirable to maintain an effectively acidic pH regime (about pH 4 or below), without being so strongly acidic as to present a hazard to the user. As will be explained in greater detail below, we have found that a combination of weakly acidic organocarboxylic acids and select volatile low molecular weight monohydric alcohol solvents provides a biocidal composition that is effective against a broad range of micro-organisms. In the preferred embodiment of this invention, low levels of anionic sulfated or sulfonated surfactant are also employed to improve the wetting and cleaning of soiled surfaces, and further enhance the biocidal properties of the composition. Co-solvents are also included in the preferred embodiment of this invention, to further improve the cleaning and evaporative properties of the invention. Such compositions were found to provide virtually no unsightly residues on cleaned surfaces, without the necessity of rinsing with fresh water after use.
Accordingly, an object of this invention is to provide a novel antimicrobial cleaning solution utilizing reduced concentrations of residual antimicrobial actives.
An additional object of this invention is to provide novel hard surface cleaning compositions that provide effective antimicrobial properties without leaving high levels of unsightly residue on the cleaning surface.
A third object of this invention is to provide novel hard surface cleaning compositions that provide effective acid-based antimicrobial chemistries in a pH regime which is generally regarded as safe for consumer household use.
A further object is to provide a method of reducing microbial pathogens from a surface while cleaning the surface without leaving highly visible deposits on the surface.
It has now been discovered that the use of low levels of select organocarboxylic acids and specific volatile monohydric alcohol solvents provides a cleaning composition with superior antimicrobial properties compared to formulations containing only similar levels of organocarboxylic acid. Preferred compositions also contain very low levels of anionic sulfated or sulfonated surfactants to improve formulation wetting and cleaning properties on soiled surfaces and to further enhance biocidal activity. Co-solvents are also included in the preferred embodiment of this invention, to further improve the cleaning and evaporative properties of the invention. Moreover, when these compositions are used as cleaners on hard surfaces, they leave virtually no unsightly residue upon wiping and drying.
This invention is directed to an antimicrobial cleaning composition comprising from about 0.01 to about 0.4 percent by weight of at least one organocarboxylic acid selected from those having an ionization constant of from about 1xc3x9710xe2x88x922 to about 1xc3x9710xe2x88x925 in water at 25xc2x0 C., wherein the pH of the composition is from about 2 to about 4 at 25xc2x0 C. In addition, the composition of the invention contains from about 0.25 percent to about 5 percent by weight of at least one sparingly water-soluble, volatile monohydric alcohol solvent selected from the group consisting of aliphatic alcohols or a glycol ether.
In a preferred mode, the inventive composition also contains from about 0.01 to about 0.3 percent by weight of at least one anionic sulfated or sulfonated surfactant selected from the group consisting of alkyl sulfates, alkyl sulfonates, and aryl sulfonates with alkyl or aryl substituents.
In another preferred mode of the invention, the composition also contains from about 0.5 to about 10 percent by weight of at least one low molecular weight monohydric alcohol co-solvent which is completely miscible with water at 25xc2x0 C.
In yet another preferred mode of the invention, the composition contains from about 0.05 to 1 percent by weight of a 1,2-alkanediol, a 1,3-alkanediol, a 2,3-alkane diol, or a 2,4-alkane diol, such diols having a molecular weight of less than 200 atomic mass units.
Other objects, advantages, and features of the present invention shall be apparent to one of skill in the art after review of the specifications and claims.
This invention is directed towards a low residue antimicrobial cleaning composition consisting of at least one organocarboxylic acid, comprising from about 0.01 to about 0.4 percent by weight of an aqueous solution. The organocarboxylic acid is selected from the group consisting having an ionization constant of from about 1xc3x9710xe2x88x922 to about 1xc3x9710xe2x88x925 in water at 25xc2x0 C., wherein the pH of the composition is from about 2 to about 4 at 25xc2x0 C. It is also believed that this pH range provides some cleaning efficacy against low to moderate levels of hard-water (mineral soil) stains.
Exemplary organocarboxylic acids include citric acid, lactic acid, glycolic acid, gluconic acid, glucoheptonic acid, malic acid, malonic acid, glutaric acid, succinic acid, adipic acid, formic acid, oxalic acid, acetic acid, propanoic acid, benzoic acid, phthalic acid, and mixtures thereof. Other suitable organocarboxylic acids include low molecular weight polymeric organocarboxylic acids (molecular weight average, Mw, below about 60,000 atomic mass units) such as poly(acrylic acid) and poly(maleic) acid homopolymers and copolymers. Examples include Goodrite K-7058(copyright) available from BF Goodrich Speciality Chemicals, and Belclene 901(copyright) available from FMC Corporation.
Preferably, the composition contains between from about 0.05 to 0.3 percent by weight of an acid selected from the group consisting of citric acid, lactic acid, glycolic acid, malic acid, acetic acid, propanoic acid, and polymeric acids with molecular weight averages from about 1000 to about 10,000 atomic mass units, and mixtures thereof.
The inventive composition also contains from about 0.25 percent to about 5 percent by weight of at least one sparingly water-soluble, volatile monohydric alcohol solvent selected from the group consisting of aliphatic alcohols or a glycol ether. The term xe2x80x9csparingly water solublexe2x80x9d is defined as having less than about 10 percent by weight solubility in water at 25xc2x0 C. Exemplary solvents include n-butanol, benzyl alcohol, phenylethanol, and glycol ethers selected from the group consisting of:
(1) Rxe2x80x94Oxe2x80x94CH2CH2xe2x80x94OH, where R is n-pentyl, n-hexyl, phenyl, or benzyl;
(2) Rxe2x80x2xe2x80x94Oxe2x80x94(CH2CH2xe2x80x94O)2OH, where Rxe2x80x2 is n-hexyl, phenyl, or benzyl;
(3) Rxe2x80x3xe2x80x94Oxe2x80x94CH2CHxe2x80x94(CH3)OH, where Rxe2x80x3 is n-butyl, n-pentyl, n-hexyl, phenyl, or benzyl; and
(4) Rxe2x80x3xe2x80x94O(CH2CHxe2x80x94(CH3)O)2H, where Rxe2x80x3 is n-butyl, n-pentyl, n-hexyl, phenyl, or benzyl.
Thus, in accordance with the above, the preferred solvent is an ethylene or diethylene glycol ether wherein R comprises n-pentyl, n-hexyl, phenyl, or benzyl, and Rxe2x80x2 comprises n-hexyl, phenyl, or benzyl; or a propylene or dipropylene glycol ether wherein Rxe2x80x3 comprises n-butyl, n-pentyl, n-hexyl, phenyl, or benzyl. Preferably, the inventive composition contains from about 50 to about 95 percent by weight of the solvent required to achieve it""s maximum solubility in water at 25xc2x0 C.
A preferred mode of this invention is directed to an antimicrobial composition comprising from about 0.01 to about 0.3 percent by weight of at least one anionic surfactant selected from the group consisting of:
(i) linear C8 to C16 alkyl sulfates;
(ii) C8 to C16 alkyl sulfonates
(iii) C8 to C16 alkyl benzenesulfonates;
(iV) C8 to C16 alkyl diphenyloxide disulfonates; and
(v) C4 to C16 alkylated naphthalene sulfonates.
The anionic surfactant is preferably an alkyl sulfate such as sodium lauryl sulfate (hereinafter xe2x80x9cSLSxe2x80x9d), an alkyl benzene sulfonate such as sodium dodecyl benzene sulfonate (hereinafter xe2x80x9cSDBSxe2x80x9d), or mixtures thereof. Other preferred anionic surfactants include disodium dodecyldiphenyloxide disulfonates such as those sold under the tradename Dowfax 2A1(copyright) from The Dow Chemical Company, or sodium n-octylsulfonate such as Bioterge PAS-8(copyright) from the Stepan Company.
Most preferably, the anionic surfactant is selected from those utilizing an alkali metal or ammonium cation, due to their relatively low cost. The most preferable alkali metal is sodium because of the widespread commercial availability and low cost of the sodium salts of these anionic surfactants. The acid forms of the aryl sulfonate anionic surfactants may also be employed. Preferred examples include dodecylbenzene sulfonic acid and dodecyldiphenyloxide disulfonic acid, such as those sold under the tradename Biosoft(copyright)S-100 from the Stepan Company or Dowfax 2A0(copyright) from The Dow Chemical Company.
Completely water miscible monohydric volatile co-solvents are included in these aqueous solutions by the addition, for example, of ethyl or propyl alcohol or completely water soluble glycol ethers. These solvents are employed to enhance the cleaning and evaporative properties of the compositions. Exemplary volatile solvents include ethyl and propyl alcohols, and glycol ethers selected from the group consisting of the following formulae:
(a) Rxe2x80x94Oxe2x80x94CH2CH2xe2x80x94OH, where R is ethyl, propyl, or butyl
(b) Rxe2x80x2xe2x80x94Oxe2x80x94(CH2CH2xe2x80x94O)2OH, where Rxe2x80x2 is ethyl, propyl, butyl, or pentyl
(c) Rxe2x80x3xe2x80x94Oxe2x80x94CH2CHxe2x80x94(CH3)OH, where Rxe2x80x3 is methyl, ethyl, or propyl
(d) Rxe2x80x2xe2x80x3xe2x80x94Oxe2x80x94(CH2CHxe2x80x94(CH3)O)2H, where Rxe2x80x2xe2x80x3 is methyl or ethyl
Exemplary glycol ethers include diethylene glycol mono-ethyl ether, available under the tradename Carbitol(copyright) from Union Carbide Corp.; and dipropylene glycol methyl ether, available under the trade name Dowanol DPM(copyright) from The Dow Chemical Company. When employed, one or more co-solvents are typically present in a total amount ranging from about 0.5 to about 10 percent by weight; preferably about 1 to about 5 percent by weight of the solution.
The preferred mode of this invention may also contain low levels of a 1,2-alkanediol, a 1,3-alkanediol, a 2,3-alkanediol, or a 2,4-alkanediol, such diols having a molecular weight of less than 200 atomic mass units. Exemplary diols include 1,2-propanediol, 2-methyl-2,4-pentanediol, and 1,2-octanediol. When employed, the diols are typically present in an amount from about 0.05 to about 1 percent by weight; preferably about 0.1 to about 0.5 percent by weight of the solution. The inclusion of the above alkane-diols improves the cleaning and evaporative properties of the invention.
The inventive solution can be aqueous or non-aqueous. Aqueous solutions are most preferred. The aqueous solution of this invention will generally contain an amount of water in the range from about 85 to about 99 percent and preferably, from about 90 to about 98 percent by weight.
Other additives known in the cleaning and disinfecting arts may be included in the inventive solution. Such additives include, for example, wetting agents (i.e. fluorosurfactants), colorants, fragrances, preservatives and stabilizers.
Additionally, this invention is also directed to a method of cleaning with simultaneously reducing the microbial contamination present on a surface by the application of the composition to the substrate by wiping, mopping, spraying, misting, dripping, or the like. The method may comprise a single step of applying the solution onto the substrate without direct physical removal, or may comprise both application and removal steps such as spraying followed by wiping with a cloth. The method may also comprise the use of a cloth wipe substrate having been premoistened with the antimicrobial solution of the present invention.
Modes Of Carrying Out The Invention
The examples which follow are intended as an illustration of certain preferred embodiments of the invention. The amount of a component in a composition is expressed in percent by weight in an aqueous solution unless otherwise noted. In the examples which follow, various substances utilized are abbreviated as follows: